This is three days of foundation work but they are nearly finished after the first week.   The delay is mostly because of the hand digging required because the backhoe didn't go deep enough towards the rear of the lot which is higher than the front.  The albañil (mason)says the backhoe guy wasn't experienced enough ... but the albañil left me to oversee the digging and I didn't know what they had planned.

So here they are laying out the perimeters and finding level with the "water in the hose" trick.   The castillos (support columns) are almost a meter deeper than the bottom of the foundation and spaced 5 meters or less